The increased use of rechargeable batteries for portable electronics and electric vehicles motivates the need for smaller, lighter, safer, and more durable batteries (Goodenough, J. B. et al, Basic Research Needs for Electrical Energy Storage, Office of Basic Energy Sciences, Department of Energy, 2007). The capacity of a lithium-ion battery is determined largely by its electrode materials, which are currently graphite for the anode and a lithium-metal-oxide (LiMO2, M=Co, Ni, Mn) or lithium-metal-phosphate (e.g., LiFePO4) for the cathode (Tarascon, J. M. et al., Nature 2001, 414, 359-367; Whittingham, M. S., Chem. Rev. 2004, 104, 4271-4301). Among the many promising replacements for the anode, silicon has the highest theoretical capacity (4009 mAh/g), which corresponds to the maximum uptake of 21 Li per 5 Si atoms (Goward, G. R. et al., J. Alloys Compd. 2001, 329, 82-91). However, silicon suffers from a large volumetric expansion of up to 300% and amorphization during lithiation, which introduces challenges for its use as a stable battery anode upon repeated cycling (Ding, M. S. et al., J. Electrochem. Soc. 2001, 148, A1196-A1204; Liang, M. H. et al., J. Mater. Chem. 2009, 19, 5871-5878; Kim, T. et al., J. Power Sources 2006, 162, 1275-1281; Wang, W. et al., J. Power Sources 2007, 172, 650-658; Zhang, Y. et al., Electrochim. Acta 2006, 51, 4994-5000).
Another important factor for battery performance is the structure and composition of the solid electrolyte interphase (SEI) formed on the electrodes. In the case of graphite, the SEI layer helps protect the electrode and electrolyte from degradation, but also can be deleterious by impeding lithiation processes (Peled, E. et al., J. Electrochem. Soc. 1979, 126, 2047-2051). Methods have been proposed to create an artificial SEI by depositing thin films of lithium-ion conducting materials, leading to modest improvements in capacity and increases in battery lifetime (Kim, Y. J. et al., J. Electrochem. Soc. 2003, 150, A1723-A1725; Fey, G. T. et al., J. Power Sources 2009, 189, 837-840; Li, G. et al., J. Power Sources 2008, 183, 741-748; Ren, M. et al., J. Phys. Chem. C 2008, 112, 5689-5693; Vidu, R. et al., Ind. Eng. Chem. Res. 2004, 43, 3314-3324; Wang, Z. X. et al., J. Electrochem. Soc. 2002, 149, A466-A471; Jung, Y. S. et al., J. Electrochem. Soc. 2010, 157, A75-A81).
Composite materials hold promise for next generation lithium-ion battery anodes. In particular, silicon-carbon composites are now commonly explored as anode materials because the Si component can provide a significantly enhanced capacity, while the C component can act simultaneously as an active electrode and an electronic bridge between the particles (Liu, W. R. et al., J. Electrochem. Soc. 2005, 152, A1719-A1725; Ng, S. et al., Angew. Chem., Int. Ed. 2006, 45, 6896-6899; Kim, H. et al., Nano Lett. 2008, 8, 3688-3691; Wang, W. et al., ACS Nano 2010, 4, 2233-2241; Cui, L. et al., Nano Lett. 2009, 9, 3370-3374; Chou, S. et al., Electrochem. Commun. 2010, 12, 303-306; Chan, C. et al., ACS Nano 2010, 4, 1443-1450; Winter, M. et al., Monatsh. Chem. 2001, 132, 473-486; Zhao, C. et al., Adv. Energy Mater. 2011, 1, 1079-1084). Architectures of Si and C that concurrently provide high capacity and long lifetime are therefore of great interest to the lithium battery community (Krishnan, R. et al., Nano Lett. 2010, 11, 377-384). On the other hand, silicon carbide (SiC) is an inert refractory material that is not traditionally viewed as a promising candidate for Li-ion battery electrodes (Capitani, G. C. et al., Am. Mineral. 2007, 92, 403-407). For example, SiC has been identified as the inactive matrix in Si—SiC “active-inactive” composite anodes in previous Li-ion battery studies (Kim, S. et al., J. Power Sources 2004, 130, 275-280).
In recent years, 6H-SiC (space group P63mc) has received increased interest as a substrate for epitaxial growth of graphene (Yu-Ming, L. et al., IEEE Electron Device Lett. 2011, 32, 1343-1345; Kedzierski, J. et al., IEEE Trans. Electron Devices 2008, 55, 2078-2085; Zhou, S. Y. et al., Nat. Mater. 2007, 6, 770-775; Emtsev, K. V. et al., Nat. Mat. 2009, 8, 203-207). In particular, it has been found that high temperature annealing of SiC (0001) leads to the formation of epitaxial graphene at the surface (EG/SiC) with low defect density and superlative performance in high frequency electronic devices. The interface between epitaxial graphene and the underlying SiC substrate is carbon-rich and possesses a surface reconstruction designated as (6√3×6√3)R30°; Berger, C., J. Phys. Chem. B 2004, 108, 19912-19916; Berger, C. et al., Science 2006, 312, 1191-1196; Emtsev, K. V. et al., Phys. Rev. B 2008, 77, 155303). Recent studies of epitaxial graphene on SiC, where Li is vapor deposited on the surface, have shown evidence for Li diffusion through graphene into the subsurface (6√3×6√3)R30° region leading to Li—Si bonding (Virojanadara, C. et al., Phys. Rev. B 2010, 82, 205402). It has also been shown that Li can be ion implanted into SiC interstitial sites, and the Li diffusion constants have been measured (Virdis, S. et al., ISOLDE Collaboration, J. Appl. Phys. 2002, 91, 1046-1052; Linnarsson, M. K. et al., Mater. Sci. Eng., B 1999, 61-2, 275-280)
It is therefore desirable to provide a method for substantial enhancement of the electrochemical lithiation capacity of traditionally inert SiC via surface graphitization.